The present invention relates to flexible covers or tarping systems for open-topped containers. The invention most particularly concerns an apparatus adapted for use with an open-topped container bed on a land vehicle, such as a dump truck. More specifically, the invention pertains to a mechanism for restraining the flexible cover or tarp when the vehicle is moving.
Many hauling vehicles, such as dump trucks, include open-topped containers used for hauling or storing various materials. In a typical dump truck application, the dump body is used to haul a variety of particulate material, such as gravel and the like, as well as organic materials, such as grain or produce.
Depending upon the nature of the materials stored in the open-topped container, it is often desirable to provide a cover for the container. A cover is particularly valuable when the containers are part of a vehicle, such as a dump truck. Rigid covers are well known that may be hinged from one end of the container body and pivoted from an open to a closed position. While rigid covers may be acceptable for stationary containers, the same is usually not true for land vehicles. In this industry, the rigid covers have given way to flexible cover systems. Systems of this type utilize a flexible tarpaulin that can be drawn from a stowed position at one end of the container, to a deployed position covering the open top of the vehicle container or bed. The flexible cover or tarpaulin is preferable in this arena because it can be easily stowed when the cover is not necessary, such as when a dump truck is being loaded. In addition, the flexible cover is generally easier to deploy than a rigid cover.
A variety of flexible cover or tarping systems have been developed that are geared toward particular hauling vehicle applications. One such tarping system is the Easy Pull.RTM. System of Aero Industries, Inc. The Easy Paul.RTM. System includes a flexible tarp that is wound around a spool at one end of the container body. A rope attached to the free end of the tarp can be used to unwind the tarp from the roller and draw the tarp along the length of the vehicle container bed.
Another cover system particularly suited for open-topped containers on hauling vehicles, is the Easy Cover.RTM. Tarping System also of Aero Industries, Inc. The Easy Cover.RTM. Tarping System includes a U-shaped bail that is pivotably mounted to the base of the vehicle container body. The horizontal section of the U-shaped bail is attached to the tarp, while the free ends of the vertical elements are pivotably mounted. In one application, the Easy Cover.RTM. System allows the tarp to be manually pulled in a sweeping arc over the container load.
Another particular application of a similar tarping system is generally depicted in FIG. 1. A vehicle 10, such as a dump truck, can include an open-topped container body 11. The body preferably includes a top rail 11b around its upper perimeter, and a number of vertically oriented support ribs 11a.
A tarpaulin cover 13 is depicted in FIG. 1 in its deployed configuration spanning the length of the container body 11. The tarp can be preferably stowed by winding onto a tarp roller 14 at the forward end of the vehicle. Both the tarp 13 and the roller 16 can be of a variety of known constructions, such as the Easy Cover.RTM. Tarping System.
In the particular illustrated vehicle application, a bail member 16 is mounted to the truck body 11 at a pivot mount 17. The bail member 16 is attached to the free end of the tarp 13 and arranged so that the pivoting travel of the bail member 16 moves the tarp from its stowed to its deployed position. The bail member 22 is preferably U-shaped, and includes a pair of elongated arms 18 connected to the vehicle at the pivot mount 17.
It is understood that the vehicle 10 shown in FIG. 1 represents one type of hauling vehicle that utilizes a flexible cover or tarping system. In other systems, the tarp is attached to and supported by curved bows that span the width of the truck bed. Like the system depicted in FIG. 1, the bow-type tarping system can be manually or mechanically deployed, typically by pulling the end of the tarp and sliding the bows along runners mounted to the top rail 11b the container body 11.
Regardless of the particular hauling vehicle application or tarp configuration, one problem that is persistently faced is the effect of air flow or wind as the vehicle is traveling. This problem becomes especially acute at high speeds. The tarpaulin 13 is affected in a number of ways by the air flow across a traveling vehicle 10. The front end of the vehicle creates turbulent air flow that travels along the length of the container body 11. This turbulence, which can be manifested by air vortices along the top rail 11b of the container body, has a tendency to lift the flexible cover 13 away from the top of the body 11. A similar result occurs due to the Bernoulli effect of the air passing over the top of the vehicle. In essence, the tarp 13 acts as an air foil, so that the air passing over the top of the tarp creates a lower pressure zone, which again results in displacing the tarp from the top of the container body 11.
All of these wind-related effects cause the tarp system and flexible cover to bellow and flap. In addition, rough road conditions can cause the tarp system, including its mechanical elements, to bounce. While this action of the tarp and the associated tarping system can be very noisy, the most deleterious effect is on the flexible cover 13 itself. The constant bellowing and flapping gradually wears the tarp down, which decreases its longevity. In addition, when the tarp 13 bellows, the load within the container body 11 is exposed to the elements.
In order to address this problem, various manually activated systems have been devised. In one common system, a web of cords are deployed over the cover 13 along the length of the container body 11. The ends of the cords can be attached to mounts fixed to the side of the body. In other systems, the bail member, such as bail member 16, can be activated to wrap the end of the cover over the end of the vehicle body. These systems can be either manually or mechanically operated, and can be tied down using a tie down rope at the end of the body.
Still other systems rely upon a complicated array of mechanical, electrical or hydraulic structures to apply a constant tension along the length of the tarp. However, in most cases, the tension along the length of the tarp does not alleviate the problem of bellowing and flapping of the side edges of the tarp along the top rail 11b of the vehicle body 11. In some cases, a tensioning cable is threaded through eyelets along the side edges of the flexible cover. These tension cables require some form of manual or mechanical intervention to tightening the cables once the cover has been deployed over the container body.
In spite of the many approaches to address the wind-related damage to the cover tarp, these wind effects remain substantially unchecked. All of the mechanical and rope-based systems have some amount of play or give that is exploited by the previously described wind effects, particularly at high vehicle speeds. Consequently, what is needed is a hold-down mechanism positively restrains the elements of the tarping system to counteract the detrimental impact of the wind rushing across and through the flexible tarp.